IIRC, that's the pose Kenshiro and Shin were in when they attacked each other with the "move of the tiger that kills the dragon" and the "move of the dragon that kills the tiger" respectively.
In the original Super Smash Bros intro, they have this going on for all of the characters. I now realize that it's probably a nod to the Hokuto no Ken show.
Half-right; it is originally Nanto Gokuto Ken, but the kanji for it was changed in the 1980s anime series and movie to remove risk of offending certain individuals at the time.